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Although wheel wabble, even with high-pressure tires, is of ancient origin and the general methods of controlling it have been well understood, its importance among present-day problems is due to the fact that the recognized specific for its treatment, namely, increasing the air-pressure in the tires, has been denied. Shimmying, as generally applied, includes wabble, or the sidewise vibration of the front wheels about the knuckle-pin, and tramping, or the bouncing of the wheels vertically, alternately on the two sides. In addition to discussing the advantages and disadvantages of the low-pressure tire, the author has enumerated the results of tests, some of which have been obtained from original research work by himself, others from the literature on the subject, with a view to determining whether shimmying is caused by defects in design, and what are the effects when certain modifications are introduced.

Reviewing briefly the history of the automotive clutch and summarizing the most interesting achievements in clutch design during recent years, the author discusses friction facings and says that the development of the asbestos-base friction-bearing has made possible the multiple-disc dry-plate and the single-plate types. For severe service, the qualifications of a satisfactory friction-facing are density of structure, together with a reasonably high tensile-strength; the coefficient of friction should be high and fairly constant over a wide range of temperature; the facing must be able to withstand high temperature without deterioration; the impregnating compound must not bleed out at high temperature; and the permeation of the impregnating solution must be complete so that the wear resistance is constant throughout the thickness of the facing. The molded and the woven types of facing are treated at length.

After referring to the recommendations made to the National Conference on Street and Highway Safety by the Committee on Motor Vehicles and the Committee's further explanation of the recommendations, the author amplifies more fully the difficulties that have arisen in the operation of the system of headlight regulations sponsored by the Illuminating Engineering Society and this Society and suggests a line of fundamental research with a view to drafting more desirable regulations. Inasmuch as road conditions have changed greatly since the regulations at present in force were first proposed, he believes that a new study of the subject might result in marked improvement. Definite control of a concentrated headlight beam, deflected below a horizontal line, as originally proposed by the Society, failed to produce the desired result, and the next step was the formulation of the regulations listed in the S.A.E. HANDBOOK.

Two points are cited as illustrating the difficulty of enforcing the present regulations, namely, (a) the variation in the angle of the headlight beam caused by the compression of the springs when the loading of the car is changed from no load to full load and (b) the variation of the tilting of the beam caused by the pitching of the car on an ordinary road, the effect being similar to that produced by flashes of lightning in a pitch-dark night. Denial is made of the author's alleged advocacy of diffused lighting and comparison is made of the distribution-curves obtained with frosted bulbs and those obtained with fairly good lamps conforming to the Society's specifications.

Various efforts have been made to apply the internal-combustion engine to self-propelled rail-cars. The greatest development along this line prior to the war was in connection with the McKeen and General Electric cars that were built from 1906 to 1914. The builders of those cars were greatly handicapped by the lack of available experience in connection with the design of gasoline engines, particularly of the larger type. Since the war a gradual development of rail-cars has taken place, starting with small converted motor trucks and gradually increasing in size and adaptability to the service, until now gasoline-electric cars of 250 hp. and about 75 ft. in length are available, while mechanically driven cars are available up to 190 continuous horsepower.

Public demand for more durability in automobile finishes has led to new developments in finishing materials and methods through cooperation of finishing materials manufacturers and automobile builders. By experimentation it has been found that certain cellulose nitrate materials, when applied over suitable under-coats, dry quickly in the air by evaporation of the solvents and leave a film that is hard and tough. Its durability is many times greater than that of the most durable finishing-varnish and, as it has been discovered that sufficient luster can be produced by rubbing and polishing the unprotected cellulose-nitrate surface, one of the large automobile production plants adopted, in July, 1923, as its standard method of finishing, the use of such a finishing coat over primer and surfacer coats, obtaining the luster by polishing the cellulose-nitrate top-coat. A number of companies have now adopted this process.

A racing airplane seems to possess a special quality that sets it distinctly apart from the conventional type of airplane; but, unless a person has at least dabbled in its design, he cannot realize the enormous amount of time, effort and ingenuity that has been expended by the designers who have made these super-speed airplanes possible. Therefore, an outline is given of the procedure adopted in designing and producing a specific model of racing airplane, as well as an outline of the yearly progress made in development. The first procedure is to allocate the work to the various members of the engineering organization. Finally, a type of design is chosen after a series of engineering conferences, and the design section studies the detail design of the component parts. A wing section that is adapted to the design already chosen is developed, and an accurate weight estimate is made of each unit part of the complete airplane.

Evolving gradually since the time when opinion prevailed that accidents are unpreventable, modern safety methods have come into being and successfully organized effort concentrated on their application in industry has accomplished an amazingly effective system of accident prevention. In the automotive industry, effort focused on preventive measures looking toward the elimination or reduction of casualties and fatalities has resulted in greatly increased conservation of life and property; but, as new conditions and new demands continually appear, it is evident that new methods, new means and new modifications must be continually in process and that putting these forces into production requires concentrated scientific study, forethought and executive ability.

Machine-repair analysis and a criticism of present-day equipment, with analytical tables based on data collected from a 5 months' study, are followed by conclusions relative to the reliability of present-day equipment. Eight types of common machine-tools are considered and the maintenance advantage of one over the other is deduced from the consolidated tables based on monthly reports. A comparison of each class of machine-tools with the others is made, as well as a summary of the weaknesses of each class from the frequency of repairs of the elementary parts. The attention of the builders is drawn to the conditions that the shop encounters with their equipment. A maintenance budget-system is described that has been installed in one plant to give the men a comparative idea of particular equipment that is running in excess of the budget time. It also serves in lieu of an inspection of the conditions of the equipment and is an indication of the time when overhauling is advisable.

Various methods of measuring the percentage of diluent in used crankcase-oils are summarized in this paper but the broader questions of deterioration of the oil due to other factors are not considered. The characteristics of viscometric methods and of steam, atmospheric and vacuum-distillation methods are discussed. It is pointed out that as dilution is not the only change the oil undergoes in service, methods based upon the assumption that oil is unchanged except by the presence of diluent may yield misleading results. Distillation methods seem best suited for this determination and those which are rational, in that the evaluation of the diluent is based on the change in the properties of the distillate as the distillation proceeds from diluent to oil, seem to promise the greatest accuracy over a wide range of diluents and oils.

Wide differences of opinion are expressed by automobile builders regarding crankcase-oil dilution. The theories advanced in explanation of dilution fail to elucidate some important facts and must therefore be regarded as unsatisfactory. From a theoretical investigation, the author determines the conditions under which the vapors of various fuels condense during the compression stroke of the engine and, as a result of such analysis, presents the theory that “surface condensation,” or the aggregation of the liquid fuel-particles on the cylinder-walls, is chiefly responsible for crankcase-oil dilution. First, suggested explanations of the dilution are presented, references to previous experiments by several authorities are stated and these are discussed. The effect of jacket-water temperature is analyzed, and whether any condensation of fuel takes place during the compression stroke of a carbureter engine is debated.

Radiation, although the subject of study for many years, is not yet thoroughly understood. The investigations of von Helmholtz 30 years ago showed that from 10 to 20 per cent of the total heat of combustion is due to radiation; but flames burning in the atmosphere show different characteristics from those subjected to a change of density in a combustion-chamber and the same conclusions do not apply. The possibility of a non-luminous flame's causing loss of heat during and after combustion was first noted by Professor Callendar in 1907. The principal theory as to the source of radiation is that it is due to the vigorous vibration of the gas molecules formed on combustion, and that, like the high-frequency radiations producing light, it is caused by chemical rather than thermal action. It has been shown that radiation emanates almost wholly from the carbon dioxide and the water molecules.

A portable instrument of the seismograph type has been designed for measuring the riding-quality of vehicles. Headings are made by a continuously revolving counter that automatically sums up the vertical displacements of a partly suspended weight. As the counter readings are a measure of the riding-quality, a large reading indicates poor riding and, conversely, a small reading indicates good riding. An arbitrary scale graduated into revolutions of the counter per mile of travel translates the readings into riding-quality; a reading of 10 indicates “very smooth,” 20, “good,” etc. The instruments have been calibrated in a special testing-machine in which the readings can be observed under an harmonic motion of fixed period and amplitude. Comparison of the riding-qualities of balloon tires and of cord tires, made on three different automobiles run over a variety of roads, shows results that are very favorable to balloon tires.

An air-spring and a steel-spring combination has a characteristic load-curve that allows maximum flexibility in the general working-range of the axle yet has an increasing resistance to dissipate large shock-loads. By varying the compression volume in the air-spring, the load curve of the combination can be made more flexible or stiffer as occasion demands. Tests show that the steel-spring vibration alone had a duration of 5½ sec. with a period of 87.2 vibrations per min.; the combination, a 3-sec. duration with 60.0 vibrations per min. Field tests of front-axle movement were made, the test apparatus for these and other tests being illustrated and explained. The maximum axle-movement either above or below the normal line is increased when using air-springs, and the subsequent rebound shows more action on the underside of the normal line, the general tendency of the air-springs being to float the chassis on a slightly higher plane at the time of rebound.

A bumper is a bar attached transversely in front of or behind a car body to prevent contact between an obstruction and the car body or to cushion the shock of collision between vehicles. The impact-bars have various sectional forms, from flat to round and from tubes to channels, and are composed of steel, wood or rubberized fabric. The attaching devices are sometimes yielding, sometimes rigid. The evolution of the bumper is shown in the records of the Patent Office. Early types had yielding attaching-parts and rigid impact-parts. These were followed by types having a rigid bar connected with the frame by only a spiral spring, by those having channel-steel impact-bars and others having round spring-steel extending from the frame-horns. A strip of rectangular spring-steel was then used by a Western blacksmith, and later a similar non-reinforced bumper appeared which was cut in two in the middle, the ends being overlapped and the overlapped parts clamped together.

This paper deals with progress in the Cooperative Fuel Research since the last report was presented to this Society. Previous tests had shown that the temperature of the jacket water exerted a major influence on the rate of dilution of crankcase oil. The reason for this influence was investigated and it was concluded that it was due to differences in the rate at which diluent was added to or eliminated from the oil-film upon the cylinder-walls, the temperature of this film being dependent upon the temperature of the jacket water. Experiments failed to show that changes in the temperature of the piston head or changes in the viscosity of the oil upon the cylinder-walls exerted a major influence upon the rate of dilution. These conditions were investigated as being probable consequences of a change in the temperature of the jacket water. Evidence is presented which demonstrates that under certain conditions the diluent may be eliminated from the oil at a fairly rapid rate.

The ascertaining of the factors that determine the riding-qualities of automobiles and the methods employed in studying these factors and the lines along which research should be directed in an effort to improve riding conditions are proposed in this paper with a view to encouraging further helpful discussion of the riding-qualities problem. Relative to the first of these questions, the factors treated in this paper comprise (a) road characteristics with respect to the vehicle; (b) the vertical, the longitudinal and the transverse motions of an automobile, as well as small vibrations or oscillations of high frequency; (c) vehicle characteristics, such as springing, accessory control, tires, wheels, chassis frame, seating, body, engine and transmission, steering-gear, brakes, heating, ventilating and lighting.

Shortage of the most desirable kinds of wood for automobile-body purposes has necessitated the substitution of second-choice woods having the essential required properties and the buying of stock for body parts in cut-up dimensions that conform in size with those now produced in the cutting-room. An investigation by the United States Forest Products Laboratory as to the species, kinds, grades, sizes and amounts used by the automotive industry shows that maple and elm comprise over one-half the total amount used and that ash and gum constitute one-half of the remainder. Although the quantity of ash used has not decreased, the increase in the production of medium and low-priced cars in the last few years bas caused a proportional increase in the demand for maple and elm.

Solicitation of sales and the delivery of the product to the customer constitute the most important operative features of the motor-truck fleet supervised by the author. Endeavor is made to install the vehicles in the various fields along standardized lines. The volume and the extent of the business and the topographical conditions of each locality determine the size and the mechanical equipment of the vehicle that is employed, and it is installed only after a study of all the conditions pertaining to its operation. Adequate training of vehicle operators, not only along mechanical lines but also as direct sales representatives of the company, is made a feature; and so is accident prevention. These interests are promoted in various standard ways and are furthered by the publication of “house organs.” After a vehicle is installed the slogan adopted is: Keep It Moving With a Pay Load.